1. Field of Invention
The present invention relates to a method for controlling a variable valve lift apparatus and a variable valve lift system, and more particularly, to a method for controlling a variable valve lift apparatus depending on given conditions by determining whether the variable valve lift apparatus is in a normal operation state depending on the given conditions and a variable valve lift system.
2. Description of Related Art
An internal combustion engine combusts fuel and air supplied to a combustion chamber to generate power.
When sucking air, an intake value is operated by driving a camshaft and air is sucked in the combustion chamber while the intake valve is opened.
Further, an exhaust valve is operated by driving the camshaft and air is exhausted from the combustion chamber while the exhaust valve is opened.
However, the optimal operation of the intake valve/exhaust valve varies depending on a rotating speed of an engine.
That is, an appropriate lift or a valve opening/closing time varies depending on the rotating speed of the engine.
Many researches to appropriately operate the valves depending on the rotating speed of the engine as described above have been conducted.
For example, research into a variable valve lift (VVL) apparatus which operates the valve as another lift depending on an engine RPM and a variable valve timing (VVT) apparatus which opens and closes the valve at an appropriate timing depending on the engine RPM has been conducted.
An oil control valve (OCV) which is used to operate the variable valve lift operation controls an operation of the variable valve lift apparatus by changing an oil passage. That is, the oil control valve (OCV) changes the oil passage to change an oil pressure transferred to the variable valve lift apparatus, thereby operating the variable valve lift apparatus.
However, in the case of the control by the oil pressure, the malfunction of the variable valve lift apparatus may occur depending on a climatic condition, such that an operation range of the variable valve lift apparatus may be reduced.
The reduction in the operation range of the variable valve lift apparatus may lead to the deterioration of engine performance and engine durability.
To solve the problems, an electric motor control scheme independent of the oil pressure may be used. However, the electric motor control scheme spends much cost and may increase power consumption to increase fuel consumption.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.